Method of cleaning oil wells



Mar. 20, 1923 R. FOGGAN METHOD OF CLEANING OIL WELLS Filed Mar. 15 19-18mm TOR 5056/7 074 1 BY Patented Mar. 20, 1923.

, UNHTED STATES ROBERT FOGGAN, 0F PLEASANTVILLE, PENNSYLVANIA.

METHOD OF CLEANING OIL Application filed March 15, 1918.- Serial No.222,719.

To all whom it may concern:

Be it known that I, ROBERT FOGGAN, a citizen of the United States. and aresident of Pleasantville, in the county of Venango and State ofPennsylvania, have invented a new and Improved Method of Cleaning OilWells, of which the following is a full, clear, and exact description.

This invention relates to the cleaning of those oil wells (hereinaftercalled non-flowing wells) which receive petroleum from the oil bearingrock under a pressure that is insuflicient to deliver the petroleum tothe surface of the ground and that would be insuflicient to do so eventhough the oil column in the well tubing should be lightened byinjection of air into the same. It has more particular (but notnecessarily lexelusive) reference to the cleaning of nonfl'owing wellswhich tap a more .or less porous oil bearing sandstone or like rockyformation.

In a non-flowing well the entrance of the petroleum into the Well cavityis apt to be rather slow at best; and ordinarily the well cavity wouldbe pumped out at intervals,

vthus exposing periodically the surface of the oil bearing rock, coatedwith petroleum, to the atmosphere. Under these conditions, the petroleumtends to deposit obstructing substances, as parafline wax, asphalt andthe like, on the well walls; and (at least when the well cavity is in amore or less porous sandstone or like rocky formation) the collection ofthese obstructing substances, increasing with the passage of time, 1sapt eventually to bring about a premature abandonment of the well;unless some 1ndustr1- ally practicable means can be found forpreserving, improving or. restoring the "'mflow of petroleum into thewell cavity.

Heretofore many proposals along varlous lines have been made. Amongother modes it has been proposed to wash the deposit ofi of the wellwalls by a solvent liquid; and

washing of the well walls with such a'liquid is employed in the presentlnventlon successfully and with advantage over all other modes withinthe rior state of the art; but in all prior plans or using a solventllqllld,

such use has been associated with oneor more nullifying or counteractingfeatures,

such as a hi h temperature, a high pressure, lack of s cient movement ofthe liquid. impractical agitating devices, water m the solvent liquid,and POSSIbly others.

the well above the oil bearing rock; and said 7 Q liquid washes the wellwall at low temperature and under low pressure, while moving about underthe influence of an agitating fluid introduced below the surface of saidsolvent liquid.

It is advantageous to use a gaseous agitating fluid, such as atmosphericair, natural gas, artificial gas, or the like, and to allow this gaseousfluid, after it has risen to the surface of the solvent liquid, to passaway through the upper part of the well outside the well tubing up whichthe petroleum is pumped.

Other things being equal, the liquid that has the greatest power ofdissolving the parafline wax, asphalt or other obstructing substance orsubstances would best be used as v the solvent liquid in the wellcavity; and gasoline, benzine, kerosene or other liquid having a greaterdissolving power than crude petroleum would ordinarily at least bepreferred to the latter for introduction through the upper part of thewell; but the use of crude petroleum in this way is not necessarilyexcluded. Crude petroleum has, however, the advantage over other solventliquids, in that a suitable body of the same can be collected in thewell cavity by direct flow from the oil bearing rock; and when thuscollected it can be moved about under the above recited conditions forthe purpose of preserving, improving or restoring the inflow ofpetroleum into said well cavity. This use of crude petroleum is withinthe scope of the invention, as expressed in one or more of thehereinafter written claims, irrespective of the manner of collecting itin the well cavity, whether by direct flow or by introduction throughthe upper part of the well. a

The accompanying drawing is a view in vertical section and elevation ofan oil well, provided with pumping appliances and also with appliancesfor use in cleaning the well in accordance with the present invention.

As shown, the upper portion 1 of the well passes through non-productiveearth and rock and has casings 8 and 10; while its lower portion 2, withwell cavity 7, is located in a more or less porous oil bearing sand rock3. A gas outlet pipe 12 leads from casing head 13 and includes a valve14.

The oil raising well tubing 15 has its lower end at or near the bottomof the well and projects at the top through the casing head 13. It hasoil admitting openings near its bottom, an oil discharging pipe 17 nearits top, and above this latter a stuffing box 18; through which last thepump rod 19 extends, for reciprocating the plunger (not shown) of thecustomary oil raising pump; this pump being constituted by said plungerand a foot valve (not shown), in connection with the working barrel,which forms part of the tubing 15, and within which the plunger isreciprocated.

The pump 6 has its discharge connected with a pipe 4, which extends downinto the well alongside the tubing 15, and opens into the well cavity 7through small apertures near the bottom of the well. It serves (withpipe 4) to introduce the agitating fluid into the solvent liquid in thewell cavity 7, and can be dispensed with when another appropriate sourceof agitating fluid is available for supplying the same to pipe 4.

Petroleum from rock 3 enters the well cavity 7 either by gravity aloneor by the joint agency of gravity and natural gas; and a non-flowingwell may either be such at the start or may result from loss of originalpressure in the oil bearing rock 3.

Petroleum is pumped up from the well cavity through the tubing anddelivered by pipe 17 to any desired receptacle. Gas can be let out ofthe well whenever desired by opening the valve 14 in pipe 12 or otherappropriate outlet.

()rdinarily, in accordance with the present invention, when a fallingoff in production is observed, the well czwity 7 (best after beingpumped out) is supplied with gasoline or other solvent liquid insufficient volume to cover the places at which the petroleum flows infrom the rock 3. without filling the well above the latter, andconsequently without forming an overlaying column of liquid whosepressure would tend substantially to hold the petroleunLin the rock 3.

The solvent liquid may well be introduced through the pipe 4; but, ifpreferred, it could be introduced otherwise, as, for example, throughthe tubing 15 or the free space within the well outside the tubing 15and the pipe 4.

The temperature of the solvent liquid in the well cavity 7 should be lowso as not to melt the parafline wax, asphalt or other obstructingsubstance on the cavity walls. Its temperature may be that whichnaturally exists in the well, or the ordinary atmospheric temperature.

An agitating fluid of low temperature, best a gaseous fluid likeatmospheric air, natural gas, or an artificial gas, say at ordinaryatmospheric temperature, is delivered by the pump 6 (or otherwise) downthe pipe 4 into the solvent liquid in the well cavity so far below thesurface of this liquid as to cause the latter tomove over and wash thecavity walls and by its solvent action to preserve, improve or restorethe inflow of the petroleum from the rock 3. A pressure producingaccumulation of gas or air above the solvent liquid is avoided by openinvalve 14.- or other suitable outlet.

he use of a gaseous fluid for the agitation is specially advantageousbecause of its lifting and mixing action, as it rises through thesolvent liquid, and its capacity forvaporizing and carrying with itwhatever water (if any) may be encountered by it, and also because ofits easy application and the fact that it removes itself from the wellwithout back pressure so long as its egress is not obstructed.

The pressure of the air or gas in pipe 4 need not be great; and it ispreferably only sufficient to cause a bubbling or agitation of thesolvent liquid in the well-cavity.

The gas or air which passes up and out of the well may be dischargedinto the atmosphere and lost; or it may be otherwise disposed of, as,for example, by conveyance to a suitable tank. Preferably, if the sameis saved or is conveyed for any purpose to a considerable distance, itis pumped from the well so as to avoid unnecessary pressure on thesolvent liquid in the well cavity.

After the well has been cleaned the solvent liquid can be pumped up andrecovered for use again in the well or for such other disposition, asmay be preferred.

It is believed that in some wells at least a dissolving and washing offof the deposit can usefully be effected, or the formation of suchdeposit be usefully checked, by means of a body of crude petroleumcollected in the well cavity, either by introduction through the upperpart of the well (as above described for gasoline), or by direct inflowfrom the oil bearing rock 3, and used under the above mentionedconditions.

\Vhat I claim is:

1. The method of renovating non-flowing oil wells, consisting in forcinga fluid into a liquid solvent in a well below the surface of the solventat a temperature suitably below the melting point of the substancesdeposited on the well walls and allowing it to escape so as to agitatethe solvent and cause it to move over the walls of the well and wash offthe deposit thereon.

2. The method of renovating non-flowing oil wells. consisting insupplying a solvent for the deposit on the walls of the oil bearingstratum of the well and then agitating said solvent at a temperaturesuitably below the melting point of the substances composing saiddeposit by the introduction of a fluid under pressure into the solventto agitate the latter and cause it to move ,over the walls of the wellto dissolve and wash off said deposit.

3. The method of renovating non-flowing oil wells, consisting insupplying to the well adjacent to the oil bearing stratum a quantity ofliquid superior to crude petroleum as a solvent for the deposit on thewell wall and agitating said solvent liquid at a tem perature suitablybelow the melting point of the substances composing said deposit by theintroduction of gaseous fluid so as to cause said liquid to dissolve andwash ofi the deposit on the well wall in said oil hearing stratum. I

4. The method of cleaning a non-flowing well, to preserve, improve orrestore the inflow of petroleum from the oil bearing rock into the wellcavity, in view of the tendency of the entering pertoleum'to depositobstructing substances on the walls of said Well cavity, which methodconsists (first) in introducing into the well cavity, through the upperpart of the well, a liquid that is superior to crude petroleum as asolvent of said substances, in suflicient volume to cover the places atwhich petroleum enters from said oil bearing rock, without forming anoverlying pressure producing column of solvent liquid, and (second) incausing the solvent liquid in said well cavity to wash the walls of thelatter under low pressure and at a temperature suitably below themelting point of said obstructing substances, while moving about underthe influence of an agitating fluid introduced below the surface of saidsolvent liquid, substantially as described.

5. The method of cleaning a non-flowing oil well, to preserve, improveor restore the inflow of petroleum from the oil bearing rock into thewell cavity, in view of the tendency of the entering petroleum todeposit obstructing substances on the walls of said well cavity, whichmethod consists (first) in introducing into the well cavity, through theupper part of the well, a liquid that is superior to crude petroleum asa solvent of said substances, in sufficient volume to cover the placesat which petroleum enters from said oil bearing rock, without forming anoverlying pressure producing column of solvent liquid, and (second) incausing the solvent liquid in said well cavity to wash the walls of thelatter under low pressure and at a temperature suitably below themelting point of said obstructing substances, while moving about underthe influence of an agitating fluid in gaseous form introduced below thesurface of said solvent liquid and allowed freely to escape up throughthe well outside the oil raising tubing, after rising to the surface ofsaid solvent liquid, substantially as described.

6. The method of cleaning a non-flowing oil well, to preserve, improveor restore the inflow of petroleum from the oil bearing rock into (thewell cavity, in view of the tendency of the entering petroleum todeposit obstructing substances on the walls of said well cavity, whichmethod consists (first) in collecting in said well cavity a liquid thatis a solvent of said substances in sufiicient volume to cover the placesat which petroleum enters from said oil bearing rock, without forming anoverlying pressure producing column of solvent liquid, and (second) incausing the solvent liquid in said well cavity to wash the walls of thelatter under low pressure and at a temperature suitably below themelting point of said obstructing substances, while moving about underthe influence of an agitating fluid introduced below the surface of saidsolvent liquid, substantially as described. a

7. The method of cleaning a non-flowing oil well, to preserve, improveor restore the inflow of petroleum from the oil bearing rock into thewell cavity, in view of the tendency of the entering petroleum todeposit obstructing substances on the walls of said well cavity, whichmethod consists (first) in collecting in said well cavity a liquid thatis a solvent of said substances in sufficient volume to cover the placesat which petroleum enters from said oil bearing rock, without forming anoverlying pressure producing column of solvent liquid, and (second) incausing the solvent liquid in said well cavity to wash the walls of thelatter under low pressure and at a temperature suitably below themelting point of said obstructing substances, while moving about underthe influence of an agitating fluid in gaseous form introduced below thesurface of said solvent liquid and allowed freely to escape up throughthe well outside the oil raising tubing, after rising to the surface ofsaid solvent liquid, substantially as described. ROBERT FOGGAN,

